obama administration says it's worked out most of the bugs from healthcare.gov but warns more work is needed on the troubled website. >>> and drone drop-off? amazon unveils its new plan to deliver your purchase to your doorstep in under an hour. this is the "cbs morning news" for monday, december 2nd, 2013. good morning. good to be with you. i'm anne-marie green. well, federal transportation officials have zbruchbt their investigation into the deadly crash of a new york city commuter train. at least four people were kanld 60 others injured. the metro north train was on its way from poughkeepsie to manhattan. it jumped the track as it rounded the curve. they're looking into speed, possible mechanical issues and human error. marlie hall is at the crash site. marlie, good morning. >> reporter: good morning, anne-marie. federal investigators continue to pore over this crash site this morning trying to determine what led to that deadly train derailment. investigators are trying to determine what caused a commuter train to jump the tracks, killing four and injuring more than 60. the investi